Smokers who have ankylosing spondylitis (AS) have more spinal damage than non-smokers with the same level of disease activity, according to a new Dutch study presented at the American College of Rheumatology’s annual meeting in San Diego this week. The effect is especially strong among men and in earlier phases of the disease.

Ankylosing spondylitis is a type of inflammatory arthritis that primarily affects the spine, hips and sacroiliac joints (where the spine meets the pelvis). The disease can lead to fusion of the vertebrae (the bones that make up the spine) resulting in a loss of flexibility and chronic pain. AS is more common in men than women.

For this study, the researchers analyzed data from 127 AS patients (71 percent of participants were men) over the course of 12 years. Each participant received a physical exam and X-rays every other year. Disease activity was measured by a patient's self-evaluation along with their C-reactive protein level, a blood marker of body-wide inflammation. X-ray damage was scored by two independent reviewers.

The researchers found that disease activity at one point in time was linked to greater damage on X-rays two years later.

When the researchers looked at the effect of smoking on this relationship, they found that the effect of disease activity on X-ray damage was 5.5 times greater, compared to that of non-smoking AS patients. In other words, smoking means that the same amount of disease activity leads to much more damage two years later.

When the researchers looked at men and women separately, they found that the effect of disease activity on X-ray damage was more than 13 times greater (i.e. worse) among male smokers compared to female non-smokers. (The effect of disease activity on X-ray damage was roughly the same for male non-smokers and female smokers).

“The effect of inflammation [disease activity] on radiographic progression is different for men and women – it’s worse for men. So for male smokers, it is even worse,” explains lead author Sofia Ramiro, MD, a PhD candidate in the department of clinical immunology and rheumatology at the University of Amsterdam, in the Netherlands.